Lighting effects have become a major element in theatrical and concert performances. As a result of the demand for elaborate lighting in such performances, sophisticated lighting systems have been developed such as disclosed in U.S. Pat. No. 4,392,187. This system utilizes a computer to control the position, intensity, size and color of the light beams produced by a large number of stage lights.
A particularly important aspect of lighting is that of color. Various colors must be produced by stage lights for working with a large number of scenes and performances, as well as to provide a specific effect which can be done only by a particular color of light. A number of patents have been filed which disclose various methods and apparatus for providing different colors of light. U.S. Pat. No. 3,816,739 discloses a device which provides colors by varying the intensity of red, blue and green light sources. In U.S. Pat. No. 4,319,311 a variety of colors are generated by employing replaceable gelatin color filters in front of the light sources. A further method for providing different colors of light is disclosed in U.S. Pat. No. 4,071,809, in which a color segmented disk is continuously rotated in front of a strobing light which is timed to flash as a certain color passes in front of the lamp. U.S. Pat. No. 4,488,207 discloses a light which has red, yellow and green sources that are angularly disposed with respect to two dichroic filters such that each color can be either transmitted or reflected from the dichroic filters onto an objective lens. Each of the above methods for producing colored light has some drawbacks. In many cases the number of available colors is very limited. The use of gelatin is undesirable as a color filter because the gelatin has a relatively short life. Other techniques require either bulky or complex equipment.
In previously noted U.S. Pat. No. 4,392,187there are disclosed two techniques for producing colored light. One technique provides dichroic filters in the light beam with means for pivoting the dichroic filters for generating light having different colors. The further technique disclosed in this patent for producing colored light is the use of dichroic filters mounted in color wheels. Each filter is a round member that is mounted in a wheel, with each filter spaced apart from the adjoining filters. These color wheels are rotated such that the light beam can pass through filters in one or both of the color wheels. Although this technique has proven to be successful, it still has drawbacks including difficulty of manufacture, expense and blanking of the light beam when the color wheel is rotated from one filter to another filter.
In view of the above, there exists a need for an inexpensive, reliable color wheel which can be easily manufactured, is compact and easy to use, and does not block the light beam when moving from one filter to the next.